here are the results of the tests :
Vista 32 and Win7 32 :
Tooltip position correct if tray icon visible
Tooltip at mouse position if tray icon not visible.
I think this is normal, and you could add a default if the tray icon is not visible (and position returns 0,0). Something like :
If (!xc && !yc) { xc := A_ScreenWidth - 10 yc := A_ScreenHeight - 10 }
In Win7 64 bits the tooltip is always at mouse position
Vista 64 bits is untested because we don't have it.
This is not a big issue.
Thanks for this code.